<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box1{
            width:100px;
            height:100px;
            background-color:red;
            position:fixed;
            right:50px;
            bottom:100px;

        }
        .box2{
            width:400px;
            height:400px;
            background-color:blue;

        }
        .box3{
            width:100px;
            height:100px;
            background-color:green;
            position:absolute;
            left:50px;
            top:100px;
        }
        h3{
            height:500px;
        }

    </style>
</head>
<body>
    <div class="box1"></div>
    <div class="box2"></div>
    <div class="box3"></div>
    <h3>吃饭</h3>
    <h3>吃饭</h3>
    <h3>吃饭</h3>
    <h3>吃饭</h3>
    <h3>吃饭</h3>

</body>
</html>